ᐅ Interior corner of an older building feels very cold, but the wall itself seems fine. Could it be poorly insulated?

Hello,
here is an older building with a bedroom facing east, sandstone/brick wall.

The room feels very cold, even though it is well heated (new heating system, new floor, 2 new radiators).

I have now taken thermal images of the wall with the windows using a thermal camera.

The problem is the corner of the wall. At a room temperature of 22°C (72°F), it is only 9.5°C (49°F) near the floor and rises to just 11.5°C (53°F) up to the ceiling.

The windows and the wall itself are fine.

Is there any way to improve the corner?

Corners are geometric thermal bridges. There is not much that can be done about them except for insulation. Alternatively, to prevent mold, these corners can also be additionally heated with heating cables.

@WilderSueden: this is the outside corner facing the neighboring house; the other corners are "better."

Is there any special insulation material for this corner? To reduce the feeling of cold (like a slight draft) a bit?

What does "outside corner to the neighboring house" mean? Are we talking about a semi-detached/terraced house and the partition wall?

Corners can generally be insulated from the inside as well, using insulation wedges. However, it is important – as with any interior insulation – that it is done professionally and airtight. Otherwise, you are even more likely to get mold behind the insulation. Exterior insulation is definitely the preferred option.

Are you the owner or the tenant?

The house (4 floors) belongs to my girlfriend. I live on the ground floor.

It is a detached house, an end house, between two other houses on each side. The one with the round windows.

The corner is the one facing the street, next to the neighboring house.

It's a shame that there are no more updates here.

Also, a question directed to the admins was not answered. Oh well.